1. Field of the Invention.
This invention relates to a water dispersible coating composition which comprises:
(i) an acrylic polymer having active hydrogen functionality and quaternary ammonium salt functionality; and
(ii) a blocked polyisocyanate. The water dispersible coating composition of this invention can be applied by any means known within the coatings art, but is especially suited for use in cathodic electrodeposition.
2. Description of the Prior Art.
The use of quaternary ammonium salt containing polymers as water reducible coatings has been known in the art. For example, U.S. Pat. No. 3,935,087 teaches resins prepared by reacting a portion of the hydroxyl groups of a hydroxyl-containing epoxy group-containing organic material with a partially-capped or blocked organic polyisocyanate, followed by reacting at least a portion of the epoxy groups in a manner so as to add pendant quaternary onium salt groups to render the resin water dispersible or solubilized.
U.S. Pat. No. 4,071,428 teaches electrodepositable compositions which comprise the reaction product of a polymeric tertiary amine and a 1,2 epoxy containing material in the presence of acid and/or water to form quaternary ammonium base group-containing polymers. This approach has the drawback that the epoxy could also react with other functional groups on the polymer backbone, such as hydroxyl groups or primary and secondary amine groups.